This invention relates to aqueous liquid compositions and processes using such liquids for chemically treating metal surfaces to form a coating layer thereon. The compositions are free from chromium and other heavy metals that cause serious pollution problems in some prior art treatment compositions. Coating layers formed in a process according to the invention can be effective for at least three different purposes: increasing adhesion of and corrosion protection from subsequently applied paints or other protective coatings with a largely organic matrix; without any subsequently applied protective coating, providing at least temporary protection against staining and development of white rust on zinc or zinc alloy surfaces treated in a process according to the invention; and providing sufficient lubricity to permit roll forming of sheet metals treated in a process according to the invention without the need for additional liquid lubricants such as oil.
Traditionally, most zinciferous and/or aluminiferous surfaces have been passivated by chemical treatment with aqueous liquid compositions containing at least some hexavalent chromium. Concerns about environmental pollution have led in recent years to development and disclosure of some chromium-free treatments. However, there is still room for further improvements with respect to, among other things, cost, ease of use, and versatility of coatings formed. Conventional rolling oil lubricants also can cause pollution, cost, and fire hazard problems.
Various alternative and/or concurrent objects of this invention are: (i) to provide an entirely or substantially chromium-free composition and process for passivating that will provide an adequate corrosion resistance in comparison with previously used high quality chromate containing passivating agents; (ii) to provide an economical passivating treatment; (iii) to reduce pollution potential; (iv) to provide a solid coating that provides adequate lubrication for roll forming of sheet metal without the need for supplemental organic liquid lubricant; (v) to provide paint-adhesion improvements by the same coating as is used for passivating; and (vi) to reduce costs of overall operations.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word xe2x80x9caboutxe2x80x9d in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout this specification, unless expressly stated to the contrary: percent, xe2x80x9cparts ofxe2x80x9d, and ratio values are by weight; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not preclude chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole; any counterions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention; the terms xe2x80x9cmoleculexe2x80x9d and xe2x80x9cmolexe2x80x9d and their grammatical variations may be applied to ionic, elemental, or any other type of chemical entities defined by the number of atoms of each type present therein, as well as to substances with well-defined neutral molecules; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; the term xe2x80x9cpaintxe2x80x9d includes all like materials that may be designated by more specialized terms such as lacquer, enamel, vanish, shellac, topcoat, and the like; and the term xe2x80x9cpolymerxe2x80x9d includes xe2x80x9coligomerxe2x80x9d, xe2x80x9chomopolymerxe2x80x9d, xe2x80x9ccopolymerxe2x80x9d, xe2x80x9cterpolymerxe2x80x9d, and the like.
It has been found that one or more of the objects stated above for the invention can be achieved by use of an aqueous liquid composition that comprises, preferably consists essentially of, or more preferably consists of, water and:
(A) a concentration of a component of dissolved phosphorus-containing anions;
(B) a concentration of a dissolved component selected from the group consisting of simple and complex anions containing fluorine atoms;
(C) a concentration of a component of dissolved and/or stably dispersed organic molecules including phenolic ring moieties with aminomethyl substituents thereon as more fully described in one or more of the following U.S. Patents, all of which, except for any content that may be inconsistent with any explicit statement herein, are hereby incorporated herein by reference: U.S. Pat. No. 4,376,000 of Mar. 8, 1983 to Lindert; U.S. Pat. No. 4,433,015 of Feb. 21, 1984 to Lindert; U.S. Pat. No. 4,457,790 of Jul. 3, 1984 to Lindert; U.S. Pat. No. 4,517,028 of May 14, 1984 to Lindert; U.S. Pat. No. 5,116,912 of May 26, 1992 to Lindert et al.; U.S. Pat. No. 5,068,299 of Nov. 26, 1991 to Lindert et al.; and U.S. Pat. No. 4,970,264 of Nov. 13, 1990 to Lindert et al.; and
(D) a concentration of a component of dissolved, stably dispersed, or both dissolved and stably dispersed film-forming molecules, said molecules not being part of any of immediately previously recited components (A) through (C); and, optionally, one or more of the following components:
(E) a concentration of a component of stably dispersed solid material that in isolated form has a coefficient of static friction, measured between two pieces of the solid material itself or between the solid material and cold rolled steel, that is not greater than 0.35, this solid material not being part of any of immediately previously recited components (A) through (D);
(F) a component of surfactant and/or of dispersing agent for one of components (D) or (E) that is not part of any of immediately previously recited components (A) through (E);
(G) a component of preservative agent that is not part of any of immediately previously recited components (A) through (F); and
(H) a component of colorant that is not part of any of immediately previously recited components (A) through (H).
The phrase xe2x80x9cstably dispersedxe2x80x9d when used herein to describe an insoluble component in a liquid continuous phase, as in the definitions of components (C), (D), and (E) recited above, means that the insoluble component is not spontaneously concentrated into any separate liquid or solid phase perceptible with unaided human vision to be distinct from, but in contact with, the liquid continuous phase within a period of observation of the combination of stably dispersed insoluble component and liquid continuous phase for 10 hours, or preferably, with increasing preference in the order given, for 1, 3, 5, 10, 30, 60, 90, 120, 240, or 360 days when stored without mechanical disturbance at 20xc2x0 C. in dispersed form. Molecules are to be understood as xe2x80x9cfilm formingxe2x80x9d for the purposes of this description if, when a homogeneous solution and/or suspension of the molecules in water containing at least 20% of the molecules is dried at a temperature of at least 25xc2x0 C. from a liquid film thickness not greater than 1 millimeter, a continuous and coherent film that is solid at 25xc2x0 C. is produced.
Various embodiments of the;invention include working compositions for direct use in treating metals, make-up concentrates from which such working compositions can be prepared by dilution with water and/or by mixing with other concentrate compositions, replenisher concentrates suitable for maintaining optimum performance of working compositions according to the invention, processes for treating metals with a working composition according to the invention, and extended processes including additional steps that are conventional per se, such as cold working, cleaning, rinsing, and subsequent painting or some similar overcoating process that puts into place an organic binder-containing protective coating over the metal surface treated according to a narrower embodiment of the invention. Articles of manufacture including surfaces treated according to a process of the invention are also within the scope of the invention.
Not applicable.